Various apparatus have been proposed for directing heated pressurized fluid streams, such as air, onto the surface of moving textile fabrics to alter the location of or modify the thermal properties of fibers or yarns and provide a pattern or visual and tactile surface change in such fabrics. Examples of such prior art equipment and methods of application of the pressurized fluid streams to a relatively moving material are disclosed in the following U.S. Pat. Nos: 2,110,118; 2,241,222; 2,563,259; 3,010,179; 3,403,862; 3,434,188; 3,585,098; 3,613,186.
It is believed that such prior art treatment devices as described in the aforementioned patents, because of the nature of the equipment disclosed, are not capable of producing precise, intricate, or well defined patterns of wide variety on the fabrics, but generally can only produce limited, relatively grossly defined patterns, or surface modifications of a random, non-defined nature in the materials. In utilizing high temperature pressurized streams of fluid, such as air, to impart visual and tactile surface patterns to textile fabrics containing thermoplastic materials by thermal modification of the same, it can be appreciated that highly precise control of stream pressure, temperature, and direction is required in all of the individual heated streams striking the fabric, to obtain uniformity and preciseness in the pattern ultimately formed in the fabric. In addition, there are ever present difficulties in regulating the flow of high temperature fluid streams by use of conventional valving systems to selectively control the stream flow between on or off positions in accordance with pattern control information.
More recently, apparatus has been developed for more precisely and accurately controlling and directing high temperature streams of pressurized fluid, such as air, against the surface of a relatively moving substrate material, such as a textile fabric containing thermally modifiable fibers. Such apparatus includes an elongate pressurized heated air distributing manifold having a narrow elongate air discharge slit extending across the path of fabric movement in close proximity to the fabric surface. Located within the manifold is a shim plate to control the thickness of the slit through which the heated pressurized air passes in a narrow, precisely defined stream to impinge upon the adjacent surface of the fabric. Flow of the heated air stream from the slit is controlled by the use of pressurized cool air which is directed by individual cool air supply tubes communicating with the outlet of the elongate manifold to direct cool air across the outlet at a generally right angle to its discharge axis to deflect the passage of heated air away from the substrate. Each cool air tube is provided with an individual valve and the valves are selectively turned on and off in response to signal information from a pattern source, such as a computer program, to allow the heated air stream to strike the moving fabric in selected areas and impart a pattern thereto by thermal modification of the yarns. Examples of related apparatus, and associated methods, may be found in U.S. Pat. Nos. 4,364,156, 4,393,562, and 4,471,514.
In moving the fabric from a room temperature or otherwise ambient environment to the manifold or other delivery mechanism for producing the pattern, the types of patterns are limited by the effect of pressurized hot air impinging on a relatively cooler thermoplastic material.
This limitation manifests itself in two ways. In continuing to move the substrate downstream following treatment in an environment where turbulent, relatively hot air surrounds the substrate, there is the potential that the pattern can be somewhat disturbed or disrupted by the failure of the thermoplastic material to be quickly quenched. Additionally, where small patterns are desired, the heated air stream must heat and thermally modify the substrate in the brief period of time--as determined by the pattern commands--during which the uninterrupted heated air stream is allowed to strike the substrate. Some small patterns, for example, pin dot patterns, can require the heated air to strike the substrate for such a brief period of time that the heated air cannot transfer sufficient heat to the substrate to cause the desired thermal modification to take place within the intended localized area on the substrate. This inability can result in indistinct, irregular, or imperceptible patterns.
Furthermore, because a large portion of the manifold and other pattern carving apparatus extends downstream on the path of movement by the substrate, any faults that may occur are not readily visible until at least a substantial portion of the fabric has passed through the machine. This creates a substantial amount of waste, adding to the cost of the material and reducing the efficiency in operation of the machine.
The present invention provides an improved method and apparatus for uniformly patterning a relatively moving substrate material by selective application of heated pressurized fluid streams to the surface thereof with a preheating step to heat the substrate prior to the patterning step. Also, to this end there is utilized an improved elongate pressurized heated fluid distributing manifold means having a single sheet of hot fluid discharged which is selectively subjected to pressurized cool fluid for pattering substrate materials and direct a mixture of hot and cool fluid upstream of the path of substrate movement to preheat the thermoplastic components on the fiber.
The manifold means includes an elongate manifold housing which is disposed across the path of movement of the substrate material and has a single heated fluid discharge outlet for discharging a pressurized streams of heated fluid, such as hot air, into the surface of the substrate across its width to thermally modify and alter the surface appearance of the substrate. Discharge of the streams of heated air from the manifold housing outlet is controlled by selectively subjecting a pressurized fluid, such as air, having a temperature substantially lower than the temperature of the heated air, across the discharge outlet of the slit to deflect the heated air away from the substrate. The pressurized cool air is introduced at the hot fluid discharge slit at a substantially right angle to its discharge axis by an individual cool air supply line. A control valve for each supply line is operated in accordance with pattern information to activate and deactivate the flow of pressurized cool air to the heated air discharge slot.
The apparatus of the method includes locating the manifold, and particularly the outlet for discharging the sheet of heated air, adjacent a main driven substrate support roll in such a position that the pattern being generated by the heated air is put down across the width of the substrate and immediately moved over the roll in a direction away from the apparatus such that an operator can quickly detect any patterning faults in the substrate while the substrate containing the fault is still in close proximity to the air outlet. In this manner the patterned fabric is fully visible to the operator after only a relatively short length of fabric travel.
This allows any air outlet blockages or other patterning malfunctions to be both quickly observed and quickly associated with a given specific section or sections of the manifold, thereby providing an efficient defect detection and diagnostic system, and minimizing the production of off-quality substrate.
In addition to minimizing waste, certain advantages in the substrate itself are accomplished by the preheating apparatus noted above. With the apparatus of the invention the hot pressurized air to carve the subject is deflected and cooled by control air and directed upstream along the path of movement of the substrate. In this way the substrate is preheated, preferably to a temperature less than the melting point of the substrate, e.g., pile fabric. This is to be compared with other methods where the substrate is brought to the air distributing manifold at room temperature and immediately subjected to "hot" air to carve it. Then the substrate is moved immediately to a region of "warm" turbulent air in the aftermath of the next line of print. This disrupts the pile and carved areas in non-flat fabric substrate.
By preheating the substrate and moving the substrate in a direction such that it is subjected to ambient temperature directly after the print line, where it is allowed to quench, a number of advantages are achieved. The carving is undisturbed until the substrate has cooled. The result is a cleaner carving of the fabric.
Furthermore, the speed of the substrate transport through the pattern process can be increased, the softness of the hand of fabric substrates for a given degree of carve is improved, and substrates that could not be carved before can now be carved at acceptable production rates. It is believed that these benefits occur because of the preheating step that occurs as the substrate approaches the patterning area of the apparatus. This preheating is accomplished by a mixture of hot air that impinges on the substrate, and the cool deflecting air that is used to deflect the hot air from the substrate. This air heats the substrate as it approaches the air distributing manifold. The heating continues right up to the time that a line of pattern is put down on the substrate by contact of the substrate with the heated air streams. Thus, the substrate is heated slowly from room temperature to some temperature below the melt as the substrate approaches the manifold. In the case of a substrate comprised of a textile fabric, at the time of patterning, enough heat is supplied to the fiber to cause the temperature of the fiber to exceed the temperature at which localized melting of the fiber occurs. This causes the melted portion of the fiber to thicken and undergo longitudinal shrinkage. Once subjected to the heated pressurized air the individual fibers are thermally modified and exhibit a change in visual and/or tactile character.
As a consequence of this novel invention, the maximum speed of the substrate moving through the patterning process has generally increased, the softness of the hand of textile fabric substrates for a given degree of carve has much improved, and textile fabrics that could not be carved before can now be carved at acceptable production rates. The speed of transport for a given level of carve was able to be increased due to the fact that the carve at a given temperature was deeper. In general there was an increase in speed as well as a decrease in the temperature of the air necessary for an acceptable depth of carve. This contributes to the softer hand of the carved fabric.
The softness of hand is believed to be caused by the difference in shrinking of the yarn brought about by the new method. An individual fiber that had been processed before exhibited a clubbed end, or in extreme cases a ball of remelted polymer on the end of a fiber stalk or fiber. These remelted ends were harsh to the touch. An individual fiber that had been processed with preheating, on the other hand, shows characteristically as a fiber of uniform but increased diameter that had reduced in length. These fibers maintain, until extreme shrinkage is achieved, a soft hand similar to the original fabric.
The above has been a brief description of some problems with the prior art and advantages of Applicant's invention. Other features of the invention will be perceived by those skilled in the art from the detailed discussion of the preferred embodiment which follows.